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The design of freeway entrances and exits requires managing the high operating speeds on the through lanes and the intense lane-change manoeuvres due to merging and diverging. Therefore, adequate lengths between these entrances and exits and provision of adequate speed-change lanes would help drivers execute such tasks safely. Most of the previous research has focused on analyzing operational conditions of the merge and diverge areas based on kinematic analysis of speeds and distances. However, little research has addressed the safety effects of merging and diverging and the interrelationship with geometric features. In this study, 26 interchanges were selected to quantify the effects of ramp terminal spacing and traffic volumes on safety performance through regression analysis. Negative binomial models were developed using 5 year collision data. Modelling attempts resulted in several statistically significant models relating traffic volumes and geometric features to collision frequency.

For testing the bond between asphalt pavement layers quite a variety of methods were proposed and used during the last 30 years. In many publications some of these test methods and devices were described by presenting photographs and sketches. Often photographs show the functioning of the devices only insufficiently and detailed information regarding the test devices (e.g. gap width) and test conditions (e.g. loading function, normal force) are difficult to retrieve. The following paper summarises the test methods and devices for the determination of the bond between asphalt pavement layers regarding shear testing. Direct and simple shear tests from all over the world are presented and their mode of operation shown. Furthermore, the range of applications is described and information regarding test evaluation and results are given.

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Australian field trials of the asphalt multi-integrated roller (AMIR) compactor confirmed the findings of Canadian trials. Consequently a successor to AMIR, hot-iron process asphalt compaction, was designed, fabricated, and tested in 1998 in Australia. With this technology, asphalt mixes can be compacted to equal or greater density with fewer passes than with conventional rolling. Furthermore, there is less variation in density, roller-induced cracking is eliminated, in situ permeability is much lower, and tensile strength and fatigue life are significantly higher. What occurs during the compaction of asphalt concrete mixes is described. The key to this concept is how the binder acts as a lubricant and how the granular particles are reoriented during compaction. Because of significant behavioral differences between unbound granular materials and asphalt concrete, it is suggested that asphalt compaction methods that emulate compaction of unbound granular materials are fundamentally flawed. It is proposed that the behavior of asphalt concrete during compaction may be more accurately modeled with consolidation theory, much like a fine-grained soil. Asphalt compaction is then a fluid flow problem, not the simple particle reorientation required for unbound material compaction. Therefore, the best way to achieve optimum compaction is to supply pressure over a sufficient interval of time. How fluid flow, air flow, and associated particle orientation work together to develop the desired asphalt service characteristics through pressure, contact area, temperature, and load duration are described. Results of analytical and field investigations are presented to support the proposed consolidation-fluid flow model of asphalt compaction.

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Existing sight distance models are applicable only to two-dimensional (2-D) separate horizontal and vertical alignments or simple elements of these separate alignments (vertical curve, horizontal curve). A new model is presented for determining the available sight distance on 3-D combined horizontal and vertical alignments. The model is based on the curved parametric elements that have been used in the finite element method. The elements presented are rectangular (4-node, 6-node, and 8-node elements) and triangular. These elements are used to represent various features of the highway surface and sight obstructions, including tangents (grades), horizontal curves, vertical curves, traveled lanes, shoulders, side slopes, cross slopes, superelevation, lateral obstructions, and overpasses. The available sight distance is found analytically by examining the intersection between the sight line and the elements representing the highway surface and the sight obstructions. Application of the new model is illustrated using numerical examples, and the results show that existing 2-D models may underestimate or overestimate the available sight distance. The proposed model should be valuable in establishing design standards and guidelines for 3-D highway alignments and determining the effect of various highway features on sight distance.